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 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *     http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
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package org.apache.hadoop.examples;

import java.io.BufferedReader;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.InputSplit;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.MultiFileInputFormat;
import org.apache.hadoop.mapred.MultiFileSplit;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.RecordReader;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.lib.LongSumReducer;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

 * MultiFileWordCount is an example to demonstrate the usage of 
 * MultiFileInputFormat. This examples counts the occurrences of
 * words in the text files under the given input directory.
public class MultiFileWordCount extends Configured implements Tool {

   * This record keeps <filename,offset> pairs.
  public static class WordOffset implements WritableComparable {

    private long offset;
    private String fileName;

    public void readFields(DataInput in) throws IOException {
      this.offset = in.readLong();
      this.fileName = Text.readString(in);

    public void write(DataOutput out) throws IOException {
      Text.writeString(out, fileName);

    public int compareTo(Object o) {
      WordOffset that = (WordOffset)o;

      int f = this.fileName.compareTo(that.fileName);
      if(f == 0) {
        return (int)Math.signum((double)(this.offset - that.offset));
      return f;
    public boolean equals(Object obj) {
      if(obj instanceof WordOffset)
        return this.compareTo(obj) == 0;
      return false;
    public int hashCode() {
      assert false : "hashCode not designed";
      return 42; //an arbitrary constant

   * To use {@link MultiFileInputFormat}, one should extend it, to return a 
   * (custom) {@link RecordReader}. MultiFileInputFormat uses 
   * {@link MultiFileSplit}s. 
  public static class MyInputFormat 
    extends MultiFileInputFormat<WordOffset, Text>  {

    public RecordReader<WordOffset,Text> getRecordReader(InputSplit split
        , JobConf job, Reporter reporter) throws IOException {
      return new MultiFileLineRecordReader(job, (MultiFileSplit)split);

   * RecordReader is responsible from extracting records from the InputSplit. 
   * This record reader accepts a {@link MultiFileSplit}, which encapsulates several 
   * files, and no file is divided.
  public static class MultiFileLineRecordReader 
    implements RecordReader<WordOffset, Text> {

    private MultiFileSplit split;
    private long offset; //total offset read so far;
    private long totLength;
    private FileSystem fs;
    private int count = 0;
    private Path[] paths;
    private FSDataInputStream currentStream;
    private BufferedReader currentReader;
    public MultiFileLineRecordReader(Configuration conf, MultiFileSplit split)
      throws IOException {
      this.split = split;
      fs = FileSystem.get(conf);
      this.paths = split.getPaths();
      this.totLength = split.getLength();
      this.offset = 0;
      //open the first file
      Path file = paths[count];
      currentStream = fs.open(file);
      currentReader = new BufferedReader(new InputStreamReader(currentStream));

    public void close() throws IOException { }

    public long getPos() throws IOException {
      long currentOffset = currentStream == null ? 0 : currentStream.getPos();
      return offset + currentOffset;

    public float getProgress() throws IOException {
      return ((float)getPos()) / totLength;

    public boolean next(WordOffset key, Text value) throws IOException {
      if(count >= split.getNumPaths())
        return false;

      /* Read from file, fill in key and value, if we reach the end of file,
       * then open the next file and continue from there until all files are
       * consumed.  
      String line;
      do {
        line = currentReader.readLine();
        if(line == null) {
          //close the file
          offset += split.getLength(count);
          if(++count >= split.getNumPaths()) //if we are done
            return false;
          //open a new file
          Path file = paths[count];
          currentStream = fs.open(file);
          currentReader=new BufferedReader(new InputStreamReader(currentStream));
          key.fileName = file.getName();
      } while(line == null);